In power factor control at an interconnection node of a wind farm, conventionally, a predetermined power-factor command value is determined by, for example, consultation with the grid operator so as to satisfy the range of, for example, a leading power factor of 0.95 to a lagging power factor of 0.95, and generation systems of individual wind turbines perform power factor control so as to maintain the determined predetermined power-factor command. In addition, if the power factor at the interconnection node deviates from the above range despite such control, the power factor at the interconnection node is adjusted by the opening/closing of a capacitor bank or reactors at a substation.
In addition, Patent Citation 1 discloses that a central controller for controlling the power at the interconnection node and so on transmits a uniform reactive power command to the individual wind turbines so that the individual wind turbines perform control based on the reactive power command.
Patent Citation 1:    U.S. Pat. No. 7,166,928, specification